As is well known in the art, a generator includes a housing enclosing a generally cylindrical shaped stator having an annular transverse cross section defining a longitudinally extending bore through its center. A plurality of electrical grade steel lamination are arranged to form a plurality of stator teeth extending circumferentially around the stator. The plurality of teeth are arranged to define a plurality of channels, generally referred to in the art as stator slots, which extend longitudinally over the length of the stator between adjacent teeth and are arranged to receive three electrical conductors or windings, collectively referred to as the stator windings, which are arranged in a predetermined configuration as is well known in the art. The stator winding configuration in the stator slots will be described later in detail. Each stator winding functions to provide a conductor wherein electricity is generated for distribution to the end user. A plurality of cooling passageways, typically having water flowing therethrough, extend through the stator winding for cooling it during operation. A plurality of support devices are attached to and positioned upwardly over the windings for providing structural support for the windings.
As an example of a typical portion of such a stator winding arrangement, a first stator slot typically receives two of the three windings which are positioned atop each other for forming a top and bottom winding, and these two windings extend out of the stator slot and wrap around and bend into another predetermined second stator slot in reversed positions so that the top winding in the first stator slot is the bottom winding in the second stator slot and vice versa for the other winding.
A rotor winding is wound around a rotatable, circular shaped rotor which is matingly placed in the stator bore. When in operation, the rotor rotates for inducing a voltage on the stator windings which, in turn, generates the electricity on the stator windings, as is well known in the art.
As previously stated, at each end of stator slot, each winding extends out of a stator slot, bends around the stator slot and projects into another predetermined stator slot for allowing the winding to be wound into its predetermined configuration. Due to the rigid, inflexible construction of the stator winding, the winding can't easily bend out of or into the stator slot. To provide this necessary flexibility, each stator winding is spliced adjacent the stator slot end and the exposed ends formed from this splicing are fitted with a water header which, in turn, is affixed to a header cap. The water header functions as a cable termination, and the header cap functions as a connection mechanism. A water tight seal, typically Silphos which is well known in the art, is interposed between the header cap and water header for forming a continuous, layered connection which is brazed together for forming a braze joint. The header caps are then attached to its corresponding header cap by a plurality of copper strands for forming a mated pair of header caps in contiguous series connection for re-attaching the stator winding. However, the header cap and braze joint may eventually need replacing because of the mechanical vibration, corrosion and the like of the generator.
Typically, to replace a header cap, one header cap of the mated pair is heated by an induction tool at its connection to the water header and is then pulled away from its respective water header for detaching it. The copper strands are then removed from this detached header cap for completely detaching it from the stator winding circuit.
To complete the installation, a new header cap and water tight seal are attached to the exposed water header by brazing them together and by re-connecting the header cap to the copper strands, all of which is described above. In performing this installation, a variety of tools may be used to hold the header cap to the exposed stator end. One such tool is a generally T-shaped clamping tool having an upright post with a transverse piece near its top portion. The transverse piece is adjustable perpendicularly relative to the upright post so that if adjusted to its extreme it forms a generally L shape. A clamp is attached to one end of the transverse piece in which an adjustable pin extends generally parallel to and downwardly from the transverse piece. The pin is also perpendicularly adjustable relative to the upright post. To use this tool, the tool attaches to a portion of the winding support devices at a bottom portion of the upright post for structural support. The transverse piece is adjusted so that the pin is positioned adjacent the header cap, and the pin is then adjusted so that it is in abutting contact with the header cap for holding the header cap in place during the brazing process.
Although the presently known and utilized device and method for holding the header cap to the water header during brazing are satisfactory, they are not without drawbacks. Because of the intense heat used during brazing, the force and direction applied to hold the header cap to the stator exposed end varies. This causes problems such as the thickness of the brazed connection increasing beyond specification, which results in a mechanical weak joint.
Consequently, a need exists for an improved method and device for installing a header cap on a water header of a stator coil.